<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .container div{
            width: 30px;
            height: 30px;
            border: 1px solid orangered;
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            border-radius: 100px;
            animation: move2 1s linear 0s infinite;
        }
        @keyframes move2 {
            0% {
                width: 30px;
                height: 30px;
                opacity: 1;
            }
            50% {
                width: 40px;
                height: 40px;
                opacity: .5;
            }
            100% {
                width: 50px;
                height: 50px;
                opacity: 0;
            }
        }
        .container {
            width: 30px;
            height: 30px;
            background-color: orangered;
            border-radius: 15px;
            position: relative;
        }
    </style>
</head>

<body>
    <div class="container">
        <div></div>
    </div>
</body>

</html>